Mold clamping device for injection molding machine

ABSTRACT

A mold clamping device for injection molding machines, in which a quick feed or closure ram is inserted in a mold clamping ram, and when a pair of molds is closed, said feed ram is pushed out from said clamping ram and said two rams are connected by means of a set of half nuts and a screw thread on the periphery of said feed ram engaging with each other, to attain a quick closure and tight clamping of the molds.

United States'Patent Aoki [151 3,656,877 [451 Apr. 1%, W72

[54] MOLD CLAMPING DEVICE FOR INJECTION MOLDING MACHINE [72] Inventor:

Sakaki-machi, Japan Katashi Aoki, 6037 Cam Minamijo,

[ 56] References Cited UNITED STATES PATENTS 3,465,387 9/ 1969 Allard etal ..l8/30 LV 3,505,708 4/1970 Moslo ..l8/30 LV X Primary Examiner-J.Howard Flint, Jr.

Attorney-David l-l. Semmes 57] ABSTRACT A mold clamping device forinjection molding machines, in

which a'quick feed or closure ram is inserted in a mold clamping ram,and when a pair of molds is closed, said feed ram is pushed out fromsaid clamping ram and said two rams are conn-zgf 1/00 nected by means ofa set of half nuts and a screw thread on the t periphery of said feedram engaging with each other, to attain ..l8/30 IA, 30 LV, 74/527 aquick closure and tight clamping ofthe molds 2 Claims, 8 Drawing FiguresI b 8 1 (-A The present invention relates to a direct-pressure type moldclamping device for synthetic resin molding machines. In the prior art,direct-pressure type mold clamping devices comprise a movable plate towhich one of two molds is attached and a mold clamping cylinder, two.beingunited in a body, wherein said mold clamping cylinder supported byan end housing and tie bars is moved to open and close the molds andbring about the engagement in a normal state, thus uniting the moldclamping ram and the quick feed ram virtually in a body.

effectuated strong mold clamping, the mold clamping cylinder is longerthan that used in mold clamping devices of other con-v struction becausethe same cylinder is ,used for mold closing and mold clamping. For thisreason, large molding machines requiring a long stroke and great moldclamping force must be provided with a huge mold clamping cylinder andan immense quantity of hydraulic oil with which the cylinder is filled.A long time is required for raising oil pressure inside the cylinder tothe maximum value because of the immense quantity of hydraulic oil andthe hugeness of the cylinder. A large highpressure pump is necessary forreducing the time. Moreover, as the movable plate travels over a fixeddistance, an increase in the thickness of a metal mold means a decreasein the stroke of the movable plate as much. This fact proves to bedisadvantageous to the molding of large products. The reason is that,when large products are to be molded, metal molds will naturallyincrease in thickness, while a long stroke will be required for takingout molded products from molds. A directpressure type mold clampingdevice, in which a power loss is small when oil pressure for moldclamping force is raised and the movable plate will not decrease instroke when a mold increases in thickness, has been developed. This moldclamping device is provided with a mold clamping cylinder between a moldclosing cylinder and a movable plate, the mold closing cylinder adaptedto open and close the movable plate in a free stroke and the moldclamping cylinder united with the movable plate adapted to develop themaximum clamping force. Pressure applied to the mold closing cylinder isborn by an end housing through the medium of upper and lower lockingmeans provided on a mold thickness adjusting barrel. Said locking means,each composed of a hydraulic cylinder and a semicircular locking plate,are put in a locking condition by the locking plates which are put inaction by the hydraulic cylinders which function when molds are closed,thereby uniting the mold closing cylinder and the mold thicknessadjusting barrel in a body to resist pressure.

Such a key lock type is advantageous in that, as the mold clampingcylinder is short in stroke, oil to be compressed is small in quantity,mold clamping pressure rises quickly and a high-pressure pump of largecapacity need not be used, while it is defective in that it is hardlyemployed in small molding machines because of complicated constructionof the key lock and the need of a mold thickness adjusting means forvarying the position of the key lock with every change in moldthickness.

An object of this invention is to provide a mold clamping device simplein construction and easy to manufacture and operate.

Another object of this invention is to provide a mold clamping devicecapable of positive adjustment of the engagement of a screw on a lockmember for joining a mold clamping ram and a quick feed ram (moldclosing cylinder) in a body with a screw engaged therewith without theuse of a special adjusting means.

A further object of this invention is to provide a mold clamping devicewherein a lock member for joining a mold clamping ram and a quick feedram in a body is made in the form of a pair of half-nuts, capable ofstarting both processes of high-speed mold opening and strong moldclamping.

A still further object of this invention is to provide a mold clampingdevice for starting high-speed mold opening when half-nuts are separatedcompletely from a quick feed ram and, on the other hand, for startingmold clamping when the halfnuts come in complete contact with the quickfeed ram to Detailed description of this invention will be given withreference to embodiments shown in the accompanying drawings, in which:

FIG. 1 is a partial sectional plan view of the moldclamping deviceembodying this invention;

FIGS. 2, 3 and 4 are enlarged sectional plan views showing theengagement of the tooth profile ofthe half-nuts for locking with that onthe circumferential surface of the mold closing cylinder; and

FIGS. 5 to 8 are sectional elevations taken on the line V- V of-FIG. 1,wherein FIGS. 5 and 6 show high-speed mold opening and strong moldclamping with half-nuts and microswitches and FIGS. 7 and 8 show twosimilar conditions in accordance with another embodiment.

In the drawings, 1 is a mold clamping cylinder, 2 is a mold clamping rammountedin the mold clamping cylinder 1. The mold clamping ram 2 isprovided with a pair of half-nuts 3 opposed to each other at the frontend thereof, a pair of the halfnuts 3 being moved to open and close byrods 6 in hydraulic cylinders 4. 5 is a cylindrical quick feed ram,having a screw thread (b) engaged with the screw threads a on saidhalf-nuts 3 carved on the circumferential surface thereof and a quickfeed piston 7 held inside thereof. The rod 8 of the quick feed piston 7has the end thereof connected to a disc 9 fixed at the rear end of themold clamping ram 2.

The fore end of the quick feed ram 5 is connected to a movable plate 11supported by a plurality of tie-bars 10 to have a pair of molds 13, 14disposed between the movable plate 11 and a fixed plate 12 opened andclosed or clamped by the forward and backward movement of the quick feedram 5.

In the mold clamping device of the above-mentioned composition, the moldclamping ram 2 and the quick feed ram 5 are connected to each other bythe engagement of the screws a on the half-nuts 3 with the screw b onthe quick feed ram 5 and pressure is applied to the mold clamping ram 2to clamp the molds, making it necessary for the quick feed ram 5 to bein the position where the two screws a, b are engaged securely with eachother. If the two screws a, b are not in perfect engagement with eachother when high-speed mold closing is completed and the half-nuts 3 arepressed against the screw on the quick feed ram 5, the quick feed ram 5will be pulled back toward the mold clamping ram 2 by a component forceon the slanting surface of the screw and the weight of the quick feedram and the weight of the movable plate 11 and the mold 13 connectedthereto act on the tooth face of the screw b, giving rise to'suchtroubles as wear and biting of the tooth face.

In the afore-mentioned prior device, an adjusting means is attached tothe quick feed ram 5 to adjust the position of the quick feed ram 5according to the thickness of the molds 13, 14 after they are closed.However, as a deviation of the two screws a, b from each other arisingfrom the position of the quick feed ram 5 is attributed to the toothpitch A (see FIG. 2 and 3) irrespective of the thickness of the molds13, 14, it is hard to adjust the position of the quick feed ram forperfect engagement because the amount of adjustment is slight.

In accordance with this invention, it is possible to obtain secureengagement between the two screws a, b without the use of a specialadjusting means, and also possible to adjust the position of the quickfeed ram 5 automatically when the two screws a, b are engaged with eachother irrespective of the thickness of the molds 13, 14. That is to say,a flange 15 is formed in a body with the quick feed ram 5 at theconnecting end thereof and a connecting ring 17 having a rim 16 whichforms a gap B nearly equal to the tooth thickness A of the screw withthe flange 15 is attached to the movable plate 11 on the back and at thecenter thereof, thus connecting the quick feed ram 5 separately andmovably through the connecting ring 17.

In accordance with this invention of the above-mentioned constructioneven if the quick feed ram 5 comes somewhat out of position after themolds are closed according to the thickness of the molds 13, 14,resulting in imperfect engagement of the screw on the half-nut 3 withthe screw b on the quick feed ram as shown in FIG. 3, it is possible tomove the quick feed ram 5 automatically and separately by pressureapplied to the half-nut 3 and a component force on the slanting surfaceof the screw to bring the screws a, b in perfect engagement as shown inFIG. 4. Therefore, unlike the case where the quick feed ram is fixed tothe movable plate, the half-nuts and the quick feed ram are alwaysconnected to each other under normal engagement after the molds areclosed irrespective of the thickness of the molds and the weight of thequick feed ram only acts on the tooth surfaces of the screws engagedwith each other, thus reducing such troubles as wear and biting on thetooth surfaces and eliminating the need of adjustment each time moldsare changed.

Strong mold clamping in the above-mentioned mold clamping device must bestarted after the crest of the screw a comes positively into the root ofthe screw b, producing connection under perfect engagement. If strongmold clamping is started in such a state of imperfect connection asloose and shallow engagement, the crests of the two screws a, b aresubjected to pressure and may even be bitten away in the worst case,giving rise to an unexpected accident. In high speed mold opening, onthe other hand, the quick feed ram 5 must be returned rapidly after thehalf-nuts 3 are separated completely from the quick feed ram 5,disconnecting the quick feed ram from the mold clamping ram. If highspeed mold opening is started before the half-nuts 3 are separatedcompletely, the quick feed ram 5 is prevented from returning by thehalf-nuts 3 in a state of engagement, and if it is forced to return, thecrests of the two screws a, b will be broken.

It is formed in the mind that the quick feed ram 5 or the mold clampingram 2 will be provided with a starting means, which will be actuated bythe movement of said ram to to clamp or open the molds, therebypreventing the aforementioned troubles from arising.

Since the movement of each of the aforementioned rams is utilized forstarting mold clamping or mold opening according to the abovementionedmethod, however, the next process is started upon movement of each ramto a predetermined position irrespective of the condition of theengagement of the half-nuts 3. The next process may be started while thescrews are in imperfect engagement or before they are completely movedback, giving rise to troubles as mentioned above.

In accordance with this invention, a plurality of mold clamping switchesand mold clamping switches are provided opposedly to each other on themold clamping ram to start strong mold clamping and high speed moldopening alternately by the movement of these switches and theabove-mentioned half-nuts, or pressure switches for effecting moldclamping and mold opening alternately are provided in hydraulic circuitsfor moving the half-nuts forward and backward to start strong moldclamping and high speed mold opening alternately by a rise of pressurein the hydraulic circuits coming about when said half-nuts come to astop.

In an embodiment shown in FIG. 5 and 6 in which strong mold clamping andhigh speed mold opening are effectuated by the movement of a pair ofhalf-nuts 3, a plurality of strong mold clamping switches 18 and highspeed mold opening switches 19 are provided on the upper part of a moldclamping ram 2 having holes 20 made therein, each set of two switches18, 19 being disposed opposedly to each other on each side of said holes20 and rods 21 for actuating each of the above-mentioned sets ofswitches 18, 19 are provided uprightly on the upper end of a pair of thehalf-nuts 3. The half-nuts 3 are moved toward and away from a quick feedram 5 with the medium of the rods 6 by oil pressure in hydrauliccylinders 4 fixed to the mold clamping ram 2 and when the half-nuts 3come in contact with predetermined positions, the abovementioned rods 21will press either of the switches 18, 19 to start strong mold clampingand high speed mold opening.

FIG. 5 shows the case wherein a pair of the half-nuts 3 are movedbackward to the mold clamping ram 2 by hydraulic pressure, thusdisconnecting the mold clamping ram 2 and the quick feed ram 5completely from each other to enable the quick feed ram 5 to operateseparately, the actuating rods 21 provided on the half-nuts 3 pressingthe switches 19 lying in the direction of movement by the backwardmovement of the half-nuts 3 to start high speed mold opening by means ofthe aforementioned quick feedpiston 7, the quick feed ram 5 being movedinward of the mold clamping ram to open the molds 13, 14.

FIG. 6 shows the case wherein a pair of half-nuts 3 are pushed towardthe part at the rear end and on the circumference of the quick feed ram5 which has been returned by another means, that is, toward the partthereof whereon a screw b is provided to connect the mold clamping ram 2and the quick feed ram 5 in a body by the engagement of screws a, b witheach other, the actuating rods 21 pressing the switches 18 inversely tothe above-mentioned to operate the mold clamping ram 2 to press thequick feed ram 5 united therewith in a body toward the molds.

In this case, if the screw b on the quick feed ram 5 and the screw a onthe half nut 3 get somewhat out of position for some reason or other,keeping the screws 11, b from coming into normal engagement and thequick feed ram 5 and the half-nuts 3 are connected completely under thecondition that the crests of the two screws butt to each other, theactuating rods 21 provided previously for actuating the switches onlywhen normal engagement comes about are prevented from pressing theswitches 18 completely by some gap formed, making it impossible toeffect strong mold clamping subsequently to the connection of the rams,whereby damage of the screws a, b attributed to imperfect engagement isprevented automatically.

FIG. 7 and 8 show an embodiment .in which pressure switches 23, 24 forstrong mold clamping and high speed mold opening are provided inhydraulic circuits 22, 22 to make use of a rise of pressure coming aboutwhen the half-nuts 3 are pressed against predetermined positions or cometo a stop. In FIG. 7, when hydraulic cylinders 4 are put in action bythe driving of a hydraulic device 25 to open a pair of half-nuts 3completely on either side, pressure in hydraulic circuits 22, 22 risesto actuate the high speed mold opening and closing pressure switch 23,thereby starting high speed mold opening by the function of a quick feedpiston 7 in the same way as the above-mentioned embodiment.

On the other hand, when the hydraulic device 25 is changed over to putthe hydraulic cylinders 4 in action, the half-nuts 3 will be closed andconnected to the quick feed ram 5 through the medium of the screws (1, bas shown in FIG. 8 and the strong mold clamping pressure switch 24 inthe hydraulic circuit 22 will be actuated by a rise of pressure, therebystarting strong mold clamping by the function of the mold clamping ram2.

Since each of the pressure switches 23, 24 is actuated by a rise ofpressure in the hydraulic circuits 22, 22 coming about after thehalf-nuts 3 move to effectuate strong mold clamping and high speed moldopening in accordance with the abovementioned embodiment, it isapprehended that strong mold clamping and high speed mold opening may bestarted by a rise of pressure even though the aforementioned screws a, bare in imperfect engagement, but the above-mentioned embodiment has theadvantage that the position where the pressure switches 23, 24 are setis not limited to the vicinity of the mold clamping ram 2, but they canbe set at an arbitrary position in the mold clamping device.

As this invention is so designed that processes of strong mold clampingand high speed mold opening are effectuated by the movement of thehalf-nuts for connecting the mold clamping ram and the quick mold feedram in a body or a rise of pressure resulting from a stop of thehalf-nuts as mentioned above, the starting of each process is positivelyrelated to the movement of the half-nuts, effectuating strong moldclamping and high speed mold opening only under normal condition,whereby damage of the aforementioned rams attributed to abnormalconnection or abnormal opening of the half-nuts can be prevented.

I claim:

1. A mold clamping device for injection molding machines having a pairof closable mold halves, comprising:

A an open interior mold clamping rain;

B. a quick feed ram operatively movably inserted through said moldclamping ram;

C. a pair of opposed threaded half nuts hydraulically movably mounted insaid mold clamping ram and extendable into or retractable from the openinterior thereof;

D. a screw thread on the periphery of said quick feed ram of matingconfiguration with those of said half nuts;

E. a movable plate and a fixed plate, said mold halves being disposedbetween said movable and fixed plates;

brought into perfect engagement by inward pressure applied to said halfnuts and a component force on the slanting surfaces of the respectivescrew threads in contact with one another; H. said quick feed ram, uponmold closing, being moved with respect to said mold clamping ram and thethreads of said half nuts and of said quick feed ram interengaging andinterconnecting said mold clamping and said quick feeding rams, therebydirectly pressing said quick feed ram in the direction of a mold by saidmold clamping ram. 2. A mold clamping device as claimed in claim 1,including a plurality of mold clamping switches and mold openingswitches opposedly mounted on said mold clamping ram and F. an outwardlyextending peripheral flange on said quick a feed ram;

G. a connecting ring attached to said movable plate including aninwardly extending rim spaced from said movable plate and forming a gaptherebetween, said flange being movable in said gap a distance nearlyequal to the tooth thickness of the respective screw threads and in adirection whereby the respective screw threads are said half nuts, saidswitches being actuatable by movement of said half nuts for initiatingstrong mold clamping and high speed mold opening alternately, ahydraulic circuit, said switches being operatively connected in saidcircuit, said hydraulic circuit operable for the extension andretraction of said half nuts for effectuating mold clamping and moldopening alternately, and initiating strong mold clamping and high speedmold opening alternately through pressure rise in said hydrauliccircuits upon terminations of half nut movements.

1. A mold clamping device for injection molding machines having a pairof closable mold halves, comprising: A. an open interior mold clampingram; B. a quick feed ram operatively movably inserted through said moldclamping ram; C. a pair of opposed threaded half nuts hydraulicallymovably mounted in said mold clamping ram and extendable into orretractable from the open interior thereof; D. a screw thread on theperiphery of said quick feed ram of mating configuration with those ofsaid half nuts; E. a movable plate and a fixed plate, said mold halvesbeing disposed between said movable and fixed plates; F. an outwardlyextending peripheral flange on said quick feed ram; G. a connecting ringattached to said movable plate including an inwardly extending rimspaced from said movable plate and forming a gap therebetween, saidflange being movable in said gap a distance nearly equal to the tooththickness of the respective screw threads and in a direction whereby therespective screw threads are brought into perfect engagement by inwardpressure applied to said half nuts and a component force on the slantingsurfaces of the respective screw threads in contact with one another; H.said quick feed ram, upon mold closing, being moved with respect to saidmold clamping ram and the threads of said half nuts and of said quickfeed ram interengaging and interconnecting said mold clamping and saidquick feeding rams, thereby directly pressing said quick feed ram in thedirection of a mold by said mold clamping ram.
 2. A mold clamping deviceas claimed in claim 1, including a plurality of mold clamping switchesand mold opening switches opposedly mounted on said mold clamping ramand said half nuts, said switches being actuatable by movement of saidhalf nuts for initiating strong mold clamping and high speed moldopening alternately, a hydraulic circuit, said switches beingoperatively connected in said circuit, said hydraulic circuit operablefor the extension and retraction of said half nuts for effectuating moldclamping and mold opening alternately, and initiating strong moldclamping and high speed mOld opening alternately through pressure risein said hydraulic circuits upon terminations of half nut movements.